Oxidation dye precursors are colorless compounds that undergo oxidative coupling in the presence of hydrogen peroxide to form colored molecules in the cortex of the fiber. Such precursors, namely, primary intermediates and couplers, form the basis of cosmetic products for permanently coloring hair.
In practice, oxidation hair dye products comprise two parts—a hair dye composition containing the dye precursors in a solvent system, and a developer composition that comprises an oxidizing agent, especially hydrogen peroxide. The first and second parts are mixed immediately before application to the hair, at which time the precursors are able to oxidatively couple owing to the presence of the oxidizing agent.
The final mixture as it is applied to the hair should be a thickened liquid, preferably with a thixotropic viscosity, so that it stays put on the hair and does not run or drip during the period of application. Many different thickening systems have been used for this purpose. One class of thickening agents used for this purpose is anionic amphiphilic polymers, which can be included in the acidic hydrogen peroxide developer composition. At an acidic pH, the anionic amphiphilic polymer is in its acidic form and the peroxide developer composition is a thin free flowing liquid. When the hair dye and peroxide developer compositions are mixed, the pH of the mixture is alkaline, the polymer is neutralized, and thickening is provided.
A number of patents have been issued covering the use of such polymers for thickening oxidation dyes, including the following: U.S. Pat. No. 4,776,855; U.S. Pat. No. 5,393,305; U.S. Pat. No. 5,376,146; U.S. Pat. No. 5,976,195; U.S. Pat. No. 5,988,295; U.S. Pat. No. 6,074,439; and U.S. RE 33,786, all of which are incorporated by reference thereto.
Suitable known anionic thickening polymers include, e.g., acrylates/beheneth-25 methacrylates copolymer, acrylates/steareth-20 methacrylate copolymer, and steareth-10 allyl ether/acrylates copolymer.
This method of thickening oxidative hair dye product compositions, i.e., the composition comprising a mixture of the first part hair dye composition and the second part developer composition, is advantageous because the individual first part hair dye composition and second part developer composition can each be highly aqueous, i.e., neither requires a high viscosity or specialized rheology. Accordingly, the resulting highly aqueous, thickened hair dye product composition is characterized by having high dyeing efficiency.
Disadvantageously, the anionic amphiphilic polymers tend to form an adherent polymeric film on the equipment (e.g., mixing tanks, storage tanks, etc.) used in manufacturing. These films are difficult to remove, requiring extensive cleanup procedures. For example, the use of a hot alkali solution has been used with some success. This is a particularly vexing problem when stainless steel vessels are used for formulating, e.g., hydrogen peroxide compositions, because scrubbing such vessels can scratch the surface of the vessel, requiring that the vessel be repassivated before further use.
Developer compositions are known that contain various surfactants, e.g., polyethoxylated alcohols and phenols, such as ceteareth-20 and nonoxynol-4, and anionic surfactants such as sulfated castor oil. Even when such surfactants are present in the anionic amphiphilic polymer-containing composition, the polymers tend to form adherent polymeric films and cleaning of the manufacturing vessels is a serious problem.